1. Field of Invention
The present invention relates to a background model update method, especially a method capable of dynamically adjusting background model update time or level. The accuracy of distinguishing a foreground image from the background model can be improved by adjusting the background model update time or weighting according to image variations such as brightness variation, motion variation, color variation, etc.
2. Description of Related Art
Current image sensing chip utilizes an image sensor to retrieve the light projected from an active light source and reflected by an object (such as a touch pen or a finger). The image sensing chip can generate object data according to the reflected light retrieved by the image sensor, wherein the object data for example include the brightness of the object and the gravity center position of the object relative to the image sensing chip, and a gesture or a motion of the object can be determined according to the object data. However, when the difference between the reflected light and the background image is too little and difficult to distinguish, a misjudgment usually happens.
For example, when a user wears a cloth with high reflection coefficient and enters a detection region of the image sensor, a bright and steady background image is formed in the image sensor. Thus, if the user waves his/her fingers/palm to produce a gesture for some control command, the brightness difference between the reflected fingers/palm image and the background image could be very little, and the gesture can very easily be misjudged due to such little difference.
Therefore, the present invention provides a method to update the background model by taking the environment and the action of a user into consideration; the image sensor can change the background model update time to improve the accuracy of distinguishing the foreground image from the background model according to a judgment on the user's action.